Canceled contract but they still debit and it's now affecting my credit score

I joined Mix Telematics last year when I bought a car. This year around July, they call and say my contract has expired and need to be renewed. I then asked why because it's only been a year and the contract was for 3 years. They said they will fix the issue. Later they sent me a letter of cancelation. Okay, I sent them an email enquiring about that and nobody responded. I called, they will just put you on waiting until the phone call gets cut... Come month end, they do not debit the monthly amount. I assume that the contract is really canceled but 3 months later they start sending me messages that I should pay or my details taken to Credit bureau. I have been calling them, wanting to cancel this contract because they are not professional at all, even now I was just in a call with an agent who didn't even wait to hear my problem but just demanded my ID number and then put me on hold for 30 minutes. Mix Telematics, you're so unprofessional and I'm not surprised many people are complaining. It means I'm not the only one being abused by this company